This invention relates to the catalytic, oxidative dehydrogenation of saturated carboxylic acids to their corresponding unsaturated acids. More particularly, it is directed to the production of unsaturated carboxylic acids such as methacrylic acid from saturated carboxylic acids such as isobutyric acid utilizing coated iron phosphorus oxide catalysts.
The production of unsaturated carboxylic acids from their corresponding saturated acids using iron phosphorus oxide catalysts, with or without various promoters, is disclosed in the art.
U.S. Pat. No. 3,948,959 discloses the preparation of unsaturated acids by oxidation of the corresponding saturated acid using iron phosphorus oxide catalysts promoted with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba. U.S. Pat. Nos. 3,634,494; 3,652,654; 3,855,279; 3,917,673 and and 4,029,695 disclose the preparation of unsaturated acids and esters from saturated acids and esters using iron phosphorus oxide catalysts, containing bismuth and/or lead promoters, optionally with other promoter elements, including Mn, U, Pr, Ca, Sr, and Cr. Prior art catalysts characteristically have exhibited short life and thermal instability.
Coated catalysts useful for exothermic reactions and a method of coating such catalysts are disclosed in U.S. Pat. No 4,077,912. Coated catalysts comprising the oxides of molybdenum, phosphorus, arsenic, and copper, useful for the production of methacrylic acid from methacrolein, are disclosed in U.S. Pat. No. 4,110,369.
These prior art coated catalysts are prepared by contacting an inert support with a liquid, preferably water, to produce a partially wet support and rolling the partially wet support in a powder of the catalytic material.
Coated catalysts, prepared by the above technique with either water or ethanol as the liquid wetting agent, are disclosed in copending patent application U.S. Ser. No. 221,859 by S. E. Pedersen, J. L. Callahan and H. F. Hardman directed to Mixed Metal Phosphorus Oxide Catalysts for the Oxidative Dehydrogenation of Carboxylic Acids, and assigned to our common assignee.
It is an object of the present invention to provide coated catalysts useful for the oxydehydrogenation of saturated carboxylic acids, which coated catalysts exhibit improved activity and attrition resistance.
It is a further object of the present invention to provide a process for the production of unsaturated acids from their corresponding saturated acids.